Use GitHub Actions for CI

.github/workflows/main.yml

@@ -0,0 +1,41 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+  workflow_dispatch:
+
+permissions:  # added using https://github.com/step-security/secure-workflows
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  main:
+    name:  ${{ matrix.os }} ${{ matrix.ruby }}
+    runs-on: ubuntu-latest
+    env:
+      # See https://github.com/tmm1/test-queue#environment-variables
+      TEST_QUEUE_WORKERS: 2
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: ['2.6', '2.7', '3.0', '3.1', '3.2', 'head', 'jruby-9.4']
+    steps:
+      - name: checkout
+        uses: actions/checkout@v3
+      - name: set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - name: spec
+        run: bundle exec rake spec
+      - name: ascii_spec
+        run: bundle exec rake ascii_spec
+      - name: internal_investigation
+        run: bundle exec rake internal_investigation